Because its exceptionally difficult to predict a market three years plus in advance. (which is why studios play it safe) and independent movies are highly risky, and nobody has the cash to bring them to wider release (even if they win a sundance award)
Hollywood did pray and spray investing long before the VC market hit onto it. The studios assume that the vast majority of films will not make money and that it is really hard to know which ones will do so in advance of them being made. So instead of spending a lot of time trying to select successful films, the studios try and spread the risk by investing wide and accepting that some years they will lose money. In the years where they lose money, the press then report that hollywood is in danger, whereas most of the studios have already budgeted for the losses.
No they don't invest wide. You have a few "wide" films a year. What you have is a stream of movies which are ordinary, mediocre and unsuccessful. Why fund that?